Selected Internet Protocol (IP) Traffic Offload (SIPTO) defined in the 3rd Generation Partnership Project (3GPP) is a method for shunting a specific service close to a position where a User Equipment (UE) is attached to an access network. Specifically speaking, in addition to supporting the access of a mobile core network, a mobile communication system (including a home NodeB system) can also support an IP shunt function, thereby implementing local access of a mobile terminal to other IP equipment in a home network or the internet when a radio-side network element has a capability of IP shunt and a user agrees to allow the IP shunt.
A Software Defined Network (SDN) is a novel network innovation framework, and a core technology OPENFLOW thereof is achieved by separating a network device control plane from a data plane and integrating functions of the network device control plane into an OPENFLOW controller or serving the functions of the network device control plane as an application connected to a northbound interface of the controller, thereby achieving flexible control over a network traffic and providing a good platform for innovation of the core network and the application.
Anycast refers to identification of a group of specific service hosts in an IP network via an Anycast address, wherein a message with a destination address as the Anycast address can be routed by the IP network to a host closest to a sender in the group of specific service hosts. Each source node of the Anycast corresponds to a group of receiving nodes, only one being capable of receiving the message sent by the sender.
FIG. 1 is a diagram illustrating an SDN-based SIPTO implementation system. The IP shunt is achieved by setting a shunt gateway in FIG. 1. The shunt gateway, serving as a gateway locally accessing an external network (such as the Internet), includes a Serving Gateway (S-GW) and a Local Gateway (L-GW). Based on an idea of separating a control plane from a data forwarding plane, control functions of the S-GW and a Packet Data Network Gateway (P-GW) and/or the L-GW are separated from a data forwarding function. An S-GW/P-GW/L-GW control plane function can be achieved in the controller after being software, and an interface between the control plane function and the OPENFLOW controller is an internal interface. The control plane function can also serve as an external application provided over the OPENFLOW controller, and the northbound interface is adopted as the interface between the control plane function and the OPENFLOW controller. A specific mode depends on network deployment, which is not limited in the present disclosure. Data are forwarded by a uniform user plane gateway (such as the S-GW, the P-GW and the L-GW) under the centralized control of a Controller. Meanwhile, the user plane gateway is also compatible with a conventional radio-side network element which is an Evolved NodeB (eNB) or a Home eNB (HeNB) and/or a home NodeB gateway. As shown in FIG. 1, each gateway is the uniform user plane gateway. No matter which implementation mode of the control plane function is adopted, functions of a forwarding plane and an interface between the control plane and the forwarding plane are free from any influence. Therefore, the implementation modes are no longer distinguished below in the present disclosure, and upper layer control functions except the functions of the forwarding plane are generally regarded as the controller instead.
Since the SIPTO is the method for shunting the specific service close to the position where the UE is attached to the access network, it is very important how to select the shunt gateway close to the attachment position of the user. The shunt gateway is randomly selected by the controller in a conventional method, and the shunt gateway selected in such a way is not optimal.